KR101588908B1 - Photo-detection device and image display device - Google Patents

Abstract

(EN) Provided is a compact and high - sensitivity optical detecting device. The photodetecting device 10 has the cathode terminal of the photodiodes 1 and 2 having different spectral characteristics and the photodiode 2 forming the optical filter in an open-ended state, And detects the light intensity of the desired wavelength region from the difference. Since the photodiodes 1 and 2 accumulate electric charges, even if the photocurrent is small, they can be accumulated to obtain charges required for detection. Thus, the semiconductor devices forming the photodiodes 1 and 2 can be miniaturized, . It is also possible to realize a wide dynamic range by varying the accumulation time of the electric charges in accordance with the light intensity or by intermittently driving the elements required for differential detection at the time of detecting the difference to suppress the power consumption or to average the output, It may be reduced.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a photodetector,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical detecting apparatus and an image display apparatus, and more particularly to a method of measuring the illuminance of an outside world using a light receiving element.

For example, it has been done to control the object by measuring the brightness of the outside world with an illuminometer such as adjusting the brightness of the backlight of the liquid crystal screen or automatically turning on the street lamp.

In this illuminometer, a light receiving element for converting the intensity (light intensity) of the received light into a current corresponding thereto is used.

However, since silicon (Si), which is a material of the light receiving element, has a sensitivity peak in infrared light, in order to obtain sensitivity of the sensor to light in a predetermined wavelength range such as visible light and ultraviolet light, And the two light receiving elements having different spectral characteristics such as the output canceled in other areas are combined to obtain desired spectral characteristics.

By appropriately combining light-receiving elements having different spectral characteristics in this way, it is possible to detect spectral characteristics close to the naked eye by detecting light in visible light, or to detect ultraviolet light.

As a technique for obtaining desired spectroscopic characteristics by combining two light receiving elements in this way, there is a " semiconductor optical detecting apparatus "

Patent Document 1: JP-A-1-207640

In this technique, two N-type layers having different depths are formed on a P-type substrate to form two photodiodes having different spectroscopic characteristics, and the light in the ultraviolet region is detected by taking a difference between the currents.

However, in the prior art, in order to improve the SN ratio and increase the sensitivity, it is necessary to increase the current of the light receiving element, and for this purpose, it has been necessary to increase the light receiving element itself.

When the light-receiving element is large, the IC chip on which the light-receiving element is formed is also increased in size, which makes it difficult to miniaturize the sensor.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a compact and high-sensitivity optical detecting device.

According to a first aspect of the present invention, there is provided a light-emitting device including: a light-receiving element generating an electric charge by incident light; accumulating means for accumulating the generated electric charge in the light- And an output means for outputting a charge amount of a charge corresponding to an incident light of a desired wavelength.

In the invention described in claim 2, there is provided a light-emitting device comprising a light-shielding means for shielding light other than incident light of a desired wavelength incident on the light-receiving element, wherein the outputting means comprises: And outputs the electric charge as the electric charge amount of the electric charge to be supplied to the photodetector.

According to a third aspect of the invention, there is provided the photodetecting device according to the first or second aspect of the invention, wherein the accumulating means accumulates the charges by electrically opening predetermined electrodes of the light receiving element .

In the invention according to claim 4, the predetermined electrode of the light receiving element is connected to a constant voltage source for resetting the electric charge accumulated in the light receiving element through a predetermined switch, and the accumulating means turns off the switch Thereby to electrically open the predetermined electrode. [0013] According to another aspect of the present invention, there is provided an optical detecting apparatus comprising:

According to a fifth aspect of the present invention, there is provided a photodetector as set forth in the third aspect, wherein the photodetector includes a resetting unit for resetting the charge accumulated in the light receiving element by connecting the predetermined electrode of the light receiving element to a predetermined constant voltage source Lt; / RTI >

In the invention according to claim 6, the light-receiving element includes a first light-receiving element formed with first light-shielding means for shielding light other than incident light of the desired wavelength and a second light-shielding means for shielding incident light Wherein the first light receiving element and the second light receiving element are formed by using a second light receiving element and the accumulating means accumulates the generated charges in the first light receiving element and the second light receiving element, And a difference acquiring means for acquiring a difference between the amounts of charges accumulated in the two light receiving elements, and outputs the difference as the amount of charges corresponding to the incident light of the desired wavelength .

According to a seventh aspect of the present invention, there is provided the optical detection device according to the sixth aspect, wherein the first light receiving element and the second light receiving element have the same light receiving and storage characteristics.

In the invention according to claim 8, the light-receiving element is constituted by using a first light-receiving element and a second light-receiving element having a spectroscopic characteristic different from that of the first light-receiving element, And the outputting means includes a difference acquiring means for acquiring a difference in the amount of charges accumulated in the first light receiving element and the second light receiving element, And outputting the amount of electric charge corresponding to the incident light of the wavelength as the electric charge amount of the electric charge corresponding to the incident light of the wavelength.

According to a ninth aspect of the present invention, there is provided a light-emitting device comprising: a first light-receiving element for generating electric charges by light received by light; a second light-receiving element for generating electric charges by the light received and having spectroscopic characteristics different from those of the first light- A charge accumulating means for accumulating the charges generated in the first light receiving element and the second light receiving element; a difference acquiring means for acquiring a difference between the charges accumulated in the first light receiving element and the second light receiving element; And a difference outputting means for outputting the light output from the light receiving means.

In the invention according to claim 10, the accumulating means accumulates the electric charges by electrically opening predetermined electrodes of the first light receiving element and the second light receiving element. There is provided an optical detection device as set forth in any one of the above claims.

In the invention described in claim 11, the predetermined electrodes of the first light-receiving element and the second light-receiving element are connected to a constant voltage source for resetting the charges accumulated in the light-receiving elements through a predetermined switch, And the storage means electrically opens the predetermined electrode by turning off the switch.

In the invention according to claim 12, the difference acquiring means acquires the difference of the accumulated electric charges by the predetermined inter-electrode voltage difference between the first light receiving element and the second light receiving element Or the optical detection device according to claim 11 is provided.

According to a thirteenth aspect of the present invention, the charge accumulated in the first light receiving element and the second light receiving element is reset by connecting the predetermined electrode of the first light receiving element and the predetermined electrode of the second light receiving element to a predetermined constant voltage source And a resetting means. The optical detecting device according to Claim 10,

The invention according to claim 14 is characterized in that the difference acquisition means includes driving means for driving the difference output means at a timing at which the difference output means outputs the difference, Device.

According to a fifteenth aspect of the present invention, there is provided a light-emitting device according to any one of claims 6 to 14, characterized in that it comprises mitigation means for mitigating variations in the difference output by the difference output means due to variations in the light intensity emitted by the light source The present invention also provides an optical detecting device described in the above.

According to a sixteenth aspect of the present invention, there is provided an optical detecting apparatus according to any one of the first to fifteenth aspects, characterized by comprising changing means for changing the time during which the accumulating means accumulates electric charges in accordance with the intensity of light do.

According to a seventeenth aspect of the present invention, there is provided an image display apparatus comprising: the light detecting device according to any one of claims 1 to 16; image display means for displaying an image; brightness And brightness adjusting means for adjusting the brightness of the image display means in accordance with the determined brightness.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a compact and high-sensitivity optical detecting device.

1 is a view showing an example of a structure of a semiconductor device having a photodiode formed thereon.
2 is a diagram schematically showing spectroscopic characteristics of a photodiode.
3 is a view for explaining the configuration of the light detecting device.
4 is a schematic diagram for explaining the saturation of the output of the photodiode.
5 is a diagram showing a configuration of a light detecting device according to a modification.
6 is a diagram showing a configuration of a light detecting device according to a modification.
Fig. 7 is a diagram showing a configuration of a light detecting device according to a modification. Fig.
8 is a diagram showing a structure of a semiconductor device according to another embodiment.
9 is a diagram showing a structure of a semiconductor device according to a modification.
10 is a diagram showing a structure of a semiconductor device according to another embodiment.
11 is a view showing a structure of a semiconductor device according to a modification.
12 is a diagram showing a configuration of a digitizing circuit and a digital output light detecting circuit.
13 shows a timing chart related to the digitizing circuit.
14 is a diagram showing a configuration of a digitizing circuit and a digital output light detecting circuit according to another embodiment.
15 is a timing chart related to the digitizing circuit according to another embodiment.
16 is a diagram showing an example of a semiconductor device in which a photodiode is formed.
17 is a diagram schematically showing spectroscopic characteristics using the difference of the photodiodes.
18 is a schematic diagram for explaining the saturation of the output of the photodiode.
19 is a diagram for explaining an example of shielding electromagnetic noise.

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Outline of Embodiment

[Embodiment of photodetecting device]

3) includes a cathode terminal of photodiodes 1 and 2 having different spectral characteristics, a photodiode 1 forming an optical filter, and a photodiode 2 forming a light shielding layer. And the light intensity of the desired wavelength region is detected from the difference of the electric charges accumulated in these for a predetermined period of time.

Since the photodiodes 1 and 2 accumulate electric charges, even if the photocurrent is small, they can be accumulated to obtain charges required for detection. Thus, the semiconductor devices forming the photodiodes 1 and 2 can be miniaturized, .

It is also possible to realize a wide dynamic range by varying the accumulation time of the electric charges in accordance with the light intensity or by intermittently driving the elements required for differential detection at the time of detecting the difference to suppress the power consumption or to average the output, It may be reduced.

[Embodiment of photodetecting semiconductor device]

The light to be detected is transmitted through the light receiving surface of the photodiodes 1 and 2 (Fig. 8 (a)) and a shield having conductivity is formed, whereby the photodiodes 1 and 2 Thereby suppressing the charge from being induced.

Further, by forming two kinds of filters (Fig. 10 (a)) in which the transmittance of light varies with wavelength, on the light receiving surfaces of the photodiodes 1 and 2, respectively, a difference can be formed in these spectral characteristics.

The seal and the filter can be formed of, for example, a thin film of polysilicon or a semiconductor of a predetermined conductivity type, and can be easily manufactured by inserting the manufacturing process into the semiconductor manufacturing process.

[Embodiment of Digital Output Photodetection Circuit]

A count value corresponding to the amount of charge is generated by associating the amount of charge accumulated in the photodiodes 1 and 2 with the clock, thereby converting the amount of the accumulated charge into a digital value.

Here, a method of counting the number of clock pulses until the accumulated charge changes by a predetermined amount (FIG. 12) and a method of repeating the accumulation and reset of the charges in the photodiodes 1 and 2 within the period of the predetermined reference pulse And a method of counting the number of times (FIG. 14).

Then, the output of the digitized photodiodes 1 and 2 can be calculated and the difference can be output as a digital value.

In this method, a digital value can be obtained by a simple mechanism such as a counter or a clock, and it is not necessary to use complicated logic such as an A / D converter.

(2) Details of Embodiment

The present embodiment is roughly divided into [optical detecting device], [optical detecting semiconductor device], and [digital output optical detecting circuit], and these will be sequentially described below.

In the following description, a photodiode is used as a light receiving element. For example, other elements such as a phototransistor may be used.

[Embodiment of photodetecting device]

In the conventional photodetector, the light intensity is measured by taking the difference of the current generated by the photodiode. However, in order to improve the SN ratio and obtain sufficient sensitivity, it is necessary to increase the current of the light receiving element. It was necessary to enlarge it.

Therefore, if the sensitivity is to be improved, there is a problem that the size of the semiconductor device and the IC chip on which the semiconductor device is formed becomes large, making it difficult to downsize the sensor.

Thus, in the present embodiment, a method of accumulating charge generated in the photodiode for a predetermined time and amplifying the accumulated charge by an amplifier to take a difference is used.

1 is a view showing an example of a semiconductor device in which a photodiode used in the present embodiment is formed.

The semiconductor device 6 is formed of, for example, a single crystal of silicon, and is composed of a P-type substrate 3 formed in a P-type and N-type layers 4 and 5 in an N-type region.

The N-type layers 4 and 5 are formed to extend from the surface of the P-type substrate 3 to a predetermined depth and the N-type layer 4 is formed to a position deeper than the N-type layer 5.

The N-type layer 4 and the P-type substrate 3 constitute a photodiode 1 and the N-type layer 5 and the P-type substrate 3 constitute a photodiode 2.

When light is incident on the light receiving surface (surface) of the semiconductor device 6, electrons and holes are generated in the PN junction by the energy of light, and the output can be obtained as a voltage or a current.

Since the light transmits through the N-type layer until it reaches the PN junction, the light transmittance of the N-type layer differs depending on the wavelength of the light and the thickness of the N-type layer. Therefore, the photodiodes 1 and 2 And exhibit different spectroscopic characteristics.

Here, the spectral characteristic means a corresponding relationship (dependence) between the output of the photodiode and the wavelength of the incident light, and may be referred to as spectral sensitivity or spectral sensitivity characteristics.

As described above, the photodiode 1 functions as a first light-receiving element for generating electric charges by the light received, the photodiode 2 generates electric charges by the received light, and the second light- And functions as a second light receiving element having spectroscopic characteristics.

2 is a diagram schematically showing the spectroscopic characteristics of the photodiode 1 (PD1) and the photodiode 2 (PD2). 2 is a schematic diagram for explaining the concept, it is not necessarily drawn strictly.

The vertical axis represents the output (current, voltage, etc.) generated by the photodiode, and the horizontal axis represents the wavelength of the incident light. Further, the light intensity of the incident light is assumed to be constant.

In this example, the peak wavelength of the spectral sensitivity characteristic of the photodiode 2 is on the shorter wavelength side than the photodiode 1, and the sensitivity at the peak wavelength of the photodiode 2 is made larger than that of the photodiode 1 , And the sensitivity in the infrared region (region where the wavelength is longer than approximately 700 [nm]) is the same as that of the photodiode 1.

Therefore, if the difference is taken, the output in the infrared region is canceled, and the sensitivity of the visible light region can be obtained.

Since the spectroscopic characteristics of the photodiodes 1 and 2 can be individually adjusted according to the thickness of the N-type layer and the like, the spectral characteristics of the photodiodes 1 and 2 are properly formed and the desired spectral characteristics Can be obtained.

3 is a view for explaining a configuration of the photodetector 10 according to the present embodiment.

The light detecting device 10 is used, for example, as an illuminometer for measuring the illuminance of the outside world, and is used for adjusting the brightness of the backlight in the liquid crystal display screen of the cellular phone.

Each of the photodiodes 1 and 2 is a photodiode having different spectral characteristics, and the output difference is configured to be closer to the spectral characteristic of the naked eye.

The anode terminal of the photodiode 1 is grounded and the cathode terminal thereof is connected to the amplifier 13 and to the DC power supply 19 via the switch 17.

The switch 17 is constituted by a switching element such as a transistor and turns on and off the connection between the photodiode 1 and the DC power supply 19 by a reset signal from the reset circuit 16. [

The amplifier 13 is constituted by an amplifier circuit such as an operational amplifier, detects the voltage of the cathode terminal of the photodiode 1, amplifies the voltage, and outputs the amplified signal to the difference circuit 15.

For example, the amplifier 13 has an input impedance infinite so that no current flows from the photodiode 1, and the amplifier 13 can amplify the voltage without affecting the voltage generated in the photodiode 1 have.

The DC power supply 19 is constituted by, for example, a constant voltage circuit. When the switch 17 is turned on, the cathode terminal of the photodiode 1 is set as a reference voltage.

On the other hand, when the switch 17 is turned off, the cathode terminal is electrically opened (floating state) and charges corresponding to the light intensity are accumulated in the photodiode 1.

In this case, since the photodiode 1 is biased in the reverse direction by the DC power supply 19, the voltage of the cathode terminal is lowered by the electrons generated in the photodiode 1.

In this manner, the amount of charge accumulated in the photodiode 1 can be detected as a voltage. The rate of this decrease is inversely proportional to the rate at which electrons are generated, that is, the light intensity.

When the switch 17 is turned on again, the charge accumulated in the photodiode 1 is reset to the initial state, and the voltage of the cathode terminal becomes the reference voltage.

The configurations of the switch 18, the photodiode 2 and the amplifier 14 are the same as those of the switch 17, the photodiode 1 and the amplifier 14, respectively.

The reset circuit 16 transmits reset signals to the switches 17 and 18 at predetermined intervals, and turns them on and off at the same time.

The reset circuit 16 sets the voltage of the cathode terminal of the photodiodes 1 and 2 to the reference voltage (that is, charges accumulated in the photodiodes 1 and 2) by turning on the switches 17 and 18 Reset to the initial value), and charges are accumulated in the photodiodes 1, 2 by turning off.

As described above, the reset circuit 16 and the switches 17 and 18 function as the accumulating means for accumulating the charge generated by the light receiving element by putting the terminals of the first light receiving element and the second light receiving element into the open end state , A predetermined electrode (in this case, a cathode terminal) of the first light receiving element and the second light receiving element is connected to a predetermined constant voltage source (DC power supply 19), thereby functioning as a reset means for resetting the electric charge stored in the light receiving element .

The difference circuit 15 receives the voltage output from the amplifier 13 and the amplifier 14, generates a difference between them, and outputs the difference to the roughness judging unit 12.

As described above, the difference circuit 15 functions as difference acquiring means for acquiring the difference between charges accumulated in the first light receiving element (photodiode 1) and the second light receiving element (photodiode 2) , And outputs the obtained difference to the roughness determination section 12 as the difference output means.

The difference circuit 15 is a circuit for detecting the difference between the predetermined electrodes (cathode terminals) of the first light receiving element (photodiode 1) and the second light receiving element (photodiode 2) The difference of one charge is acquired.

The roughness determination section 12 samples and acquires the difference (for example, immediately before reset) of the voltage output from the difference circuit 15 in synchronization with the reset signal of the reset circuit 16, and obtains the roughness .

The roughness determination section 12 stores, for example, the correspondence between the difference and the roughness, and thereby the roughness of the outer world can be determined.

The roughness determination section 12 is a brightness determination section that determines the brightness of the outside world by using the output of the photodetection device 10 (here, the configuration in which the roughness determination section 12 is excluded from the photodetection device 10) Function.

Although not shown, the illuminance determining section 12 is connected to, for example, a brightness adjusting section for adjusting the brightness of the backlight of the liquid crystal display device. The brightness adjusting section adjusts the brightness of the backlight Thereby adjusting the brightness of the backlight of the liquid crystal display device.

Here, the liquid crystal display device functions as an image display means for displaying an image, and the brightness adjusting section functions as a brightness adjusting means for adjusting the brightness of the image displaying means in accordance with the brightness determined by the brightness determining section 12. [

The operation of the photodetector 10 constructed as described above will be described.

First, the operation of the photodiode 1 will be described.

When the reset circuit 16 turns on the switch 17, the cathode terminal of the photodiode 1 becomes the reference voltage by the DC power supply 19, and the charge stored in the photodiode 1 becomes the initial value Reset.

Next, when the reset circuit 16 turns off the switch 17, the photodiode 1 is disconnected from the DC power supply 19 and the input impedance of the amplifier 13 is infinite, It becomes an open-ended state separated from the circuit.

In this case, as shown by the dashed outline in the drawing, the photodiode 1 acts like a condenser in the PN junction surface, and accumulates charges generated by light.

The voltage of the cathode terminal is lowered to a speed corresponding to the intensity of light by the charge accumulated in the photodiode 1 because it is biased in the reverse direction by the direct current power supply 19. [

Since the reset circuit 16 repeatedly turns on and off the switch 17, the voltage of the cathode terminal of the photodiode 1 changes from the reference voltage (charge reset) to the voltage drop (charge accumulation) → ... , And so on. This state is shown in Fig. 13 (a).

In the same manner as the photodiode 2, the reference voltage? Voltage drop? Reference voltage? , Are repeated in synchronization with the photodiode 1, and the photodiodes 1 and 2 have different spectroscopic characteristics, so that the speed at which the voltage drops is different.

Therefore, if the difference is taken by the difference circuit 15 after amplifying the output of the photodiodes 1 and 2, the difference is the difference of the charges accumulated in the photodiodes 1 and 2, that is, Value.

Thus, when the output of the difference circuit 15 is detected after a predetermined time (for example, immediately before the next reset) after the resetting, the roughness determining section 12 outputs the output of the photodiode 1 , 2) can be detected as the voltage difference, and thereby the illuminance can be determined.

As described above, in the photodetector 10, the outputs of the two photodetectors (photodiodes 1 and 2) having different spectral characteristics are connected to the input of the amplifier, and the photodetector can be put in a floating state have.

The photodetecting device 10 is a mechanism for resetting the charge of the light receiving element at regular intervals by using the DC power supply 19 and the reset circuit 16 to thereby perform charge accumulation in the light receiving element at regular intervals , And the difference between the signals amplified by the amplifier is outputted.

By obtaining the output difference of the voltages of the two light receiving elements having different spectral characteristics, desired spectral characteristics can be obtained.

Since the input voltage Vin of the amplifier is determined by the equation of Vin = Q / C from the total capacitance C of the light receiving element and the charge Q generated by the light intensity, the sensor sensitivity can be increased by reducing the capacitance of the light receiving element have.

This means that the sensitivity of the sensor is improved by miniaturization of the sensor, which is advantageous from the viewpoint of downsizing of the sensor.

The photodetecting device 10 measures the illuminance of the room, for example. This is an example, and the photodetector 10 may be used as an ultraviolet sensor, for example, by appropriately forming the spectroscopic characteristics of the photodiodes 1 and 2 It is possible.

(Modified Example 1)

The photodiodes 1 and 2 rapidly accumulate electric charge as the light to be received becomes stronger. Therefore, if the illuminance is large, the output of the photodiodes 1 and 2 may become saturated before the illuminance determining section 12 detects the output of the difference circuit 15, and there may be a case where the correct value can not be measured .

Thus, in this modified example, as the intensity of the light received becomes strong, the reset interval is shortened to shorten the charge accumulation period to prevent saturation of the photodiodes 1, 2. Thus, the dynamic range can be widened.

4A is a schematic diagram for explaining a case where the output of the photodiode 2 is saturated at the time of reset.

First, when the photodiodes 1 and 2 are connected to the DC power supply 19 to set the voltage of the cathode terminal to the reference voltage and then the switches 17 and 18 are turned off, It goes down.

It is assumed here that the voltage of the photodiode 2 is lowered faster than that of the photodiode 1 due to the difference in spectral characteristics.

In Fig. 4 (a), since the light intensity is large, the output of the photodiode 2 is saturated before reaching the reset time t1.

Assuming that the output of the difference circuit 15 is detected immediately before resetting, the roughness determining section 12 detects E1 which is a voltage according to the light intensity with respect to the photodiode 1 at the reset time t1, (2), since the output is saturated, a detection value corresponding to the light intensity can not be obtained.

4 (b), the voltage of the photodiode (in this case, the photodiode 2) on the side where the voltage drop is large is larger than a predetermined comparison reference voltage (hereinafter referred to as a comparison voltage) The resetting is performed.

In the example of Fig. 4 (b), the photodiode 2 is reset at time t2 when the photodiode 2 becomes the comparison voltage. In this case, the voltage of the photodiode 1 is E2.

Therefore, either of the photodiodes 1 and 2 can output a voltage corresponding to the light intensity.

Fig. 5 is a diagram showing a configuration of the photodetector 10a that performs the above-described operation. The same components as those in Fig. 3 are denoted by the same reference numerals, and a description thereof will be simplified or omitted.

The photodetector 10a further includes a DC power supply 22 and a comparator 21 in addition to the configuration of the photodetector 10.

The DC power supply 22 is a constant voltage source for providing the comparator 21 with the comparison voltage. Here, the direct current power supply 22 is configured to output a fixed comparison voltage. However, the comparison voltage may be varied so that the comparison voltage suitable for the light intensity can be selected.

The comparator 21 compares the output voltage of the photodiode 21 amplified by the amplifier 14 with the output voltage of the amplifier 14, for example, by outputting 1 when the output of the amplifier 14 is greater than the comparison voltage, (2) and the comparison voltage, and outputs the comparison result as a digital signal.

The reset circuit 16 monitors the output of the comparator 21 and detects that the voltage of the amplifier 14 has dropped to the comparison voltage (in the above example, when it is detected that the output is switched from 1 to 0) The switches 17 and 18 are reset.

Thereby, the photodetector 10a can reset the charge before the output of the photodiodes 1, 2 is saturated.

The roughness determination section 12 is configured to store the correspondence of the voltage difference, the reset interval, and the light intensity of the amplifiers 13 and 14 to determine the roughness from the output of the difference circuit 15 .

The comparator 21 and the direct current power source 22 function as a changing means for changing the time during which the accumulating means accumulates the electric charges in accordance with the light intensity.

As described above, in this modification, the light receiving element is provided with the function of changing the period in which the charge accumulates in accordance with the illuminance (specifically, the shorter the accumulation period is, the larger the illuminance is). Thus, a high dynamic range The width of the range that can be achieved).

(Modified example 2)

The amplifiers 13 and 14 and the difference circuit 15 of the optical detecting device 10 (Fig. 3) receive power supply from a power source (not shown) and perform amplification processing and differential processing.

Thus, in this modification, the amplifiers 13 and 14 and the differential circuit 15 are not always driven, and only when the roughness determination section 12 detects the difference of the photodiodes 1 and 2 and determines (I.e., only when necessary), thereby saving power consumption.

Fig. 6 is a diagram showing a configuration of the optical detecting device 10b according to the present modification.

3 are denoted by the same reference numerals, and the description thereof will be simplified or omitted.

In order to simplify the drawing, the photodiode 2, the amplifier 14, and the switch 18 are omitted.

The photodetector 10b is provided with a timer clock 31 and switches 32 and 33 in addition to the configuration of the photodetector 10.

The switch 32 and the switch 33 are constituted by switching elements such as transistors and turn on and off the power supply to the differential circuit 15 and the amplifier 13, respectively. Although not shown, the amplifier 14 also has the same switch.

The timer clock 31 is a clock for turning on and off the switches 32 and 33 at predetermined time intervals and also outputs the clock to the roughness judging section 12. [

The timer clock 31 can be formed by, for example, generating a clock of a low cycle by an internal clock by a frequency divider circuit.

The roughness determination section 12 operates in synchronization with the clock outputted by the timer clock 31 and detects the output of the difference circuit 15 at the timing when the switches 32 and 33 are turned on.

The reset circuit 16 operates in synchronism with the timer clock 31 and resets the charges of the photodiodes 1 and 2 immediately after the roughness determination section 12 performs detection, for example.

As described above, the timer clock 31, the switches 32 and 33, and the switches formed in the amplifier 14 (not shown) function as a drive means for driving the differential output means at the timing at which the differential output means outputs the difference have.

As described above, the photodetecting apparatus 10b is configured so that the amplifiers 13 and 14 and the differential circuit 15 are provided only when the roughness determining section 12 detects and judges the difference between the outputs of the photodiodes 1 and 2 The power consumption can be reduced as compared with the photodetector 10.

(Modification 3)

The present modification reduces the influence of the flicker of the light source.

(Flashing) at a cycle of 50 [Hz] or 60 [Hz], for example, to a light source such as a fluorescent lamp. This phenomenon is called flicker.

When the light intensity of the light source in which the flicker is present is measured in the photodetector 10 (FIG. 3), the measured value of the illuminance changes depending on the position of the blinking moment when the roughness determination section 12 detects the difference.

For example, cellular phones and the like are often used in a room illuminated by a fluorescent lamp, so that it is necessary to be able to appropriately measure the light intensity even in the presence of flicker.

Thus, in this modification, the influence of the flicker is alleviated by time-averaging the difference between the photodiodes 1 and 2. [

Fig. 7 is a diagram showing the configuration of the photodetector 10c with flicker countermeasure. 3 are denoted by the same reference numerals, and the description thereof will be simplified or omitted.

In order to simplify the drawing, the photodiode 2, the amplifier 14, and the switch 18 are omitted.

The photodetector 10c is configured to include an integration circuit 41 between the difference circuit 15 and the roughness determination section 12 in the configuration of the photodetector 10. The difference circuit 15, Is integrated in the integrating circuit (41).

The integration circuit 41 integrates the output of the difference circuit 15 with respect to time and outputs the obtained integral value. Since the integral value is a cumulative value of a plurality of detection values, the variation of the difference is alleviated by averaging.

As described above, the integrating circuit 41 functions as a mitigating means for mitigating variations in the difference of the difference circuit 15 when the light intensity emitted by the light source fluctuates due to flicker or the like.

The illuminance determining section 12 is operated in cooperation with the reset signal of the reset circuit 16. When the reset circuit 16 resets the reset circuit 16 a predetermined number of times after the integration circuit 41 starts integration, Value.

When the illumination determining section 12 detects the illumination, the integration value of the integrating circuit 41 is initialized to 0, and the like.

As described above, in the present embodiment, even if the output of the difference circuit 15 is varied by the flicker, the output values are averaged by adding the measured values a plurality of times in the integrating circuit 41, Value can be obtained.

In this modification, integration is used to suppress the influence of the flicker, but any method may be used that can alleviate the deviation of the detection value by the flicker in some way.

The following effects can be obtained by the present embodiment and modifications described above.

(1) Charges generated by light received by the photodiodes 1 and 2 can be accumulated.

(2) The desired spectral characteristics can be obtained by taking the difference between charges generated by the two photodiodes 1 and 2 having different spectral characteristics.

(3) The amount of charge generated in the photodiodes 1, 2 can be detected by the voltage.

(4) Since the light intensity is measured by the electric charges accumulated in the photodiodes 1 and 2, a large photocurrent is not required, and the photodiodes 1 and 2 can be miniaturized.

(5) Since the sensitivity of the photodiodes 1 and 2 can be made small, the area of the photodiodes 1 and 2 can be reduced, and a low-cost sensor can be realized.

(6) The reset interval of the charges accumulated in the photodiodes 1 and 2 can be changed according to the intensity of the external light, and a wide dynamic range can be realized.

(7) The power consumption can be saved by driving the amplifiers 13 and 14 and the differential circuit 15 only when necessary.

(8) By reducing the influence of the flicker by the integrating circuit 41, the influence of the flicker can be reduced.

(9) An IC (integrated circuit) having two light-receiving elements having different spectral characteristics, an amplifier connected to the output of the light-receiving element, and a mechanism for resetting the charge of the light-receiving element at regular intervals after putting the light- Thus, a small illuminance sensor can be obtained by accumulating charge in the light receiving element at regular intervals and outputting the difference between the signals amplified by the amplifier.

[Embodiment of photodetecting semiconductor device]

Although the semiconductor device 6 having the structure shown in Fig. 1 can be used in the optical detection device 10, it is also possible to use a semiconductor device having a structure different from that of the semiconductor device 6 shown in Fig.

Hereinafter, another type of semiconductor device applicable to the photodetector 10 will be described.

(First Embodiment of Photodetecting Semiconductor Device)

The photodetecting device 10 accumulates charges on the photodiodes 1 and 2 to measure the illuminance. Therefore, there is a possibility that the influence of the electromagnetic wave from the outside affects the measurement result as compared with the case where the difference of the current is taken as in the conventional case.

Therefore, in the present embodiment, a thin film electrode having optical transparency is disposed on the photodiode to shield the photodiode from external electromagnetic noise (for example, commercial wave or electromagnetic wave noise generated from electric equipment).

8A is a diagram showing the structure of the semiconductor device 6a according to the present embodiment.

The semiconductor device 6a is a photodetecting semiconductor device and the N type layers 4 and 5 having different thicknesses are formed on the P type substrate 3 like the semiconductor device 6.

Here, the photodiode 1 includes a semiconductor substrate (P-type substrate 3) composed of a semiconductor of a first conductivity type (P-type in this case) and a second conductive (The N-type layer 4) made of a semiconductor (here, N-type) semiconductor and the photodiode 2 functions as a first light receiving element composed of a semiconductor substrate (P-type substrate 3) And a second conductive layer (N-type layer 5) of a second conductivity type semiconductor formed from the surface of the semiconductor substrate to a depth deeper than a predetermined depth.

On the upper surfaces of the N-type layers 4 and 5, thin film-like P-type layers 51, 51, ... are formed.

Since the P-type layer 51 has transparency with respect to the light to be detected and is conductive, it transmits the light for measuring the illuminance, while the electromagnetic wave entering the light receiving surface from the outside is shielded.

The P-type layer 51 can be formed at a low cost because it can be formed by a typical semiconductor manufacturing process when the semiconductor device 6a is manufactured.

As described above, light is transmitted through the surface of the first conductive layer (N-type layer 4) and the second conductive layer (N-type layer 5), and the electromagnetic wave shield layer (P- Respectively.

In addition, the P-type layer 51 can exhibit a shielding function more effectively by being grounded.

The aluminum wirings 52 and 52 connected to the n-type layers 4 and 5 are connected to the n-type layers 4 and 5 via the n + -type thick layer 55 having an n-type concentration.

A wiring through hole is formed in the P-type layer 51, and an aluminum wiring 52 is formed in the through hole.

The P-type substrate 3 is connected to the aluminum wiring 54 by a P + layer 56 having a thick P-type concentration and is grounded.

On the light-receiving surface, light-shielding aluminum (53, 53, ...) is formed in a region where the photodiode is not formed, thereby blocking light incidence.

8 (b) is a schematic diagram showing an outline of spectroscopic characteristics of the photodiodes 1 (PD1) and 2 (PD2).

The sensitivity of the photodiode 1 with a deep N-type layer 4 is better on the infrared side than the photodiode 2.

9A is a diagram showing a structure of a semiconductor device 6b according to a modification of the embodiment.

The semiconductor device 6b is formed of thin polysilicon layers 57, 57, .... The polysilicon layer 57 can also transmit the light to be detected and shield the electromagnetic wave. Further, it can be easily formed by a conventional semiconductor manufacturing process.

The other configuration is the same as that of the semiconductor device 6a, and the spectroscopic characteristic is the same as that of the semiconductor device 6a as shown in Fig. 9 (b).

As described above, in the present embodiment and the modification, a thin-film electrode (for example, polysilicon having a thickness of about 1000 [Angstroms]) having transparency on the light receiving element can be disposed to shield the electromagnetic noise from the outside .

(Second Embodiment of Photodetecting Semiconductor Device)

In the present embodiment, the depth of the N-type layer is the same, and a filter having spectral characteristics is formed on the light receiving surface, thereby causing the photodiodes 1 and 2 to have different spectral characteristics.

10A is a diagram showing a structure of the semiconductor device 6c according to the present embodiment.

The N-type layer 7 of the photodiode 2 is formed at the same depth as the N-type layer 4. Therefore, the spectral characteristics due to the depth of the N-type layer are the same in the photodiode 1 and the photodiode 2.

On the other hand, a polysilicon layer 61 is formed on the upper surface of the N-type layer 4, and a polysilicon layer 62 thicker than the polysilicon layer 61 is formed on the upper surface of the N-type layer 7. The other configuration is the same as that of the semiconductor device 6.

As described above, in the semiconductor device 6c, the filter layer (polysilicon layer 61) in which the transmittance of light changes with the wavelength of light is formed on the surface of the first conductive layer (N-type layer 4) (The polysilicon layer 62) having a dependency different from that of the filter layer is formed on the surface of the n-type layer (N-type layer 7).

As shown in Fig. 10 (b), the polysilicon has a characteristic of attenuating (cutting) light in the blue to ultraviolet region as it gets thicker. That is, a filter having a different transmittance according to the wavelength of light is formed.

Therefore, the polysilicon layer 62 has a lower transmittance of light in the blue to ultraviolet region than the polysilicon layer 61, so that the photodiode 1 and the photodiode 2 exhibit different spectral characteristics.

In this way, different spectral characteristics can be obtained by disposing polysilicon having different film thicknesses on the light receiving element.

10 (c) is a schematic diagram showing the spectroscopic characteristics of the photodiodes 1 and 2. The photodiode 2 has lower sensitivity on the side where the wavelength of light is shorter than that of the photodiode 1.

Although the thin film of polysilicon is used as a filter in the present embodiment, it is also possible to use, for example, a thin film of a P-type layer as a filter.

11A is a diagram showing a structure of a semiconductor device 6d according to a modified example of the present embodiment. In this example, a polysilicon layer is not formed on the light receiving surface of the photodiode 1, and a polysilicon layer 63 is formed on the light receiving surface of the photodiode 2.

Also in this case, since light is attenuated in the blue to ultraviolet region among the light received by the photodiode 2, the same characteristics as those of the semiconductor device 6c are exhibited as shown in Fig. 11 (b).

As described above, in the semiconductor devices 6c and 6d, the depths of the N-type layers 4 and 7 are the same, but they may be set to different depths.

By adjusting both the thickness of the filter and the thickness of the N-type layer, more various spectral characteristics can be realized.

Further, since the polysilicon layer has conductivity and also has a function of shielding electromagnetic waves, it is possible to realize both the spectroscopic characteristics of the photodiode and the shielding of electromagnetic waves.

The following effects can be obtained by the present embodiment and modifications described above.

(1) The electromagnetic wave incident on the light receiving surface can be attenuated or cut by a thin film having conductivity.

(2) By forming a filter having a different transmittance according to the wavelength of light on the light-receiving surface, spectroscopic characteristics can be imparted to the photodiode.

(3) Since the filter has conductivity, electromagnetic shielding can be performed at the same time.

[Embodiment of Digital Output Photodetection Circuit]

The outputs of the photodiodes 1 and 2 are analog values, while the light intensity detected by the photodiodes 1 and 2 is a digital device such as a cellular phone.

Therefore, it is necessary to convert the detection values by the photodiodes 1, 2 into digital signals.

However, when the output of the photodiode is converted into a digital signal, conventionally, the digital signal is converted by the A / D converter.

Such a technique is, for example, an " optical sensor circuit " disclosed in Japanese Laid-Open Patent Publication No. 11-304584.

In this technique, a plurality of reference voltages for detecting the output of the photodiode are prepared, and a reference voltage corresponding to the input range of the A / D converter is selected.

However, the use of the A / D converter increases the size of the logic and increases the scale of the circuit, resulting in an increase in the size of the IC chip, making it unsuitable for a demand for miniaturization, and also increasing manufacturing costs.

Thus, in the present embodiment, a digital output photodetection circuit that does not require an A / D converter having a large circuit scale is used by using the property that the photodiodes 1 and 2 accumulate electric charges.

(First Embodiment of Digital Output Photodetection Circuit)

In the present embodiment, the light intensity is digitized by measuring the time during which the voltage of the photodiodes 1, 2 drops, by the number of reference pulses.

12 (a) is a diagram showing a configuration of a digitizing circuit 77 for digitizing the output of the photodiode 1.

The digitizing circuit 77 is constituted by using the same components as the optical detecting device 10a shown in Fig. The same constituent elements as those in Fig. 5 are denoted by the same reference numerals, and a description thereof will be omitted or simplified.

The comparator 21 compares the output voltage of the photodiode 1 amplified by the amplifier 13 with the output voltage of the amplifier 13, for example, when the output of the amplifier 13 is larger than the comparison voltage, Compares the magnitude of the voltage with the magnitude of the comparison voltage, and outputs the comparison result as a digital signal.

The reset circuit 16 monitors the output of the comparator 21 and detects that the voltage of the amplifier 13 has dropped to the comparison voltage (in the above example, when it is detected that the output is switched from 1 to 0) The switch 17 is turned on to reset the charge of the photodiode 1.

Since the time required for the voltage of the photodiode 1 (amplified by the amplifier 13, the same applies hereinafter) to reach the comparison voltage from the reference voltage becomes shorter as the light intensity becomes larger, the reset circuit 16 is reset Is shortened.

The clock 72 generates a clock pulse, which is a pulse signal at a constant interval, and inputs the clock pulse to the counter circuit 71.

The pulse width of the clock pulse is set to be sufficiently short as compared with the time so that the time at which the voltage of the photodiode 1 reaches the comparison voltage at the reference voltage can be measured. The clock 72 functions as clock signal generating means for generating a clock signal.

The counter circuit 71 receives the input of the digital signal indicating the comparison result from the comparator 21 and receives the input of the clock pulse from the clock 72. [

Then, using these, the number of clock pulses in a period of time from when the voltage of the photodiode 1 falls to the comparison voltage from the reference voltage is counted, and the count value is output.

Since the time until the output of the photodiode 1 becomes the comparison voltage is in inverse proportion to the light intensity, the larger the light intensity is, the smaller the count value becomes, and the count value corresponding to the light intensity is obtained.

As described above, the counter circuit 71 generates a count value that generates a count value corresponding to the amount of the accumulated charge by associating the amount of the charge accumulated in the photodiode 1 with the clock signal in which the clock 72 is generated And functions as count value output means for outputting the generated count value.

The counter circuit 71 generates the count value of the number of clock signals generated until the accumulated charge changes from the initial value to the predetermined value.

13 shows a timing chart of the digitizing circuit 77. In Fig.

The output (Fig. 13 (a)) of the photodiode 1 is reset to the reference voltage by the reset signal (Fig. 13 (c)) of the reset circuit 16, The larger the value, the faster the deterioration.

The comparison result (Fig. 13 (b)) output by the comparator 21 is a signal that outputs 0 when the voltage of the photodiode 1 reaches the comparison voltage at the reference voltage, (Fig. 13 (c)).

The counter circuit 71 measures a clock pulse in which the clock 72 is generated during the period in which the comparison result of the comparator 21 is 1 (the clock pulse measurement period in Fig. 13 (d)), Output.

In this way, in the digitizing circuit 77, since the clock pulse to be measured becomes smaller as the light intensity is larger, the number of pulses corresponding to the light intensity is obtained.

12 (b) is a view for explaining a configuration of the digital output light detecting circuit 75 according to the present embodiment.

The digital output photodetecting circuit 75 is provided with a digitizing circuit 77 for digitizing the output of the photodiode 1 and a digitizing circuit 78 for digitizing the output of the photodiode 2. The configuration of the digitizing circuit 78 is the same as that of the digitizing circuit 77. [

The difference calculating section 73 receives the outputs of the photodiodes 1 and 2 converted into digital values from the digitizing circuits 77 and 78 and calculates these differences by digital processing and outputs the calculated differences as digital values do.

Thus, the difference calculating section 73 calculates the difference between the first count value corresponding to the amount of the electric charge accumulated in the first light receiving element (photodiode 1) and the second count value corresponding to the second light receiving element (The photodiode 2), and also digitally calculates the difference between the acquired first count value and the second count value And also functions as difference output means for outputting the calculated difference as a digital value.

In this way, the digital output photodetecting circuit 75 can detect the photodiodes 1 and 2 by a simple configuration using the counter circuit 71 and the clock 72 without using arithmetic logic such as an A / Can be digitized.

(Second Embodiment of Digital Output Photodetection Circuit)

In this embodiment, the light intensity is digitized by measuring the number of times the photodiodes 1 and 2 are reset within the period of the reference pulse.

This is done by measuring the amount of charge accumulated in the reference pulse period with the accumulation amount per unit as a unit, thereby associating the accumulated charge amount with the generated clock signal.

14 (a) is a diagram showing a configuration of a digitizing circuit 77a for digitizing the output of the photodiode 1.

The configuration of the digitizing circuit 77a according to the present embodiment is the same as that of the digitizing circuit 77 shown in the first embodiment, and the corresponding elements are denoted by the same reference numerals, and a description thereof will be omitted or simplified.

The configuration of the comparator 21 and the reset circuit 16 is the same as that shown in Fig. 12 (a).

The clock 72a generates a reference pulse, which is a pulse signal at a constant interval, and inputs it to the counter circuit 71. [

The pulse width of the reference pulse is sufficiently larger than the time for the reset circuit 16 to reset the photodiode 1 so that the reset circuit 16 can measure the number of times the voltage of the photodiode 1 reaches the comparison voltage at the reference voltage It is set long.

Further, if the reference pulse width is made longer than the period of the flicker (about 200 [ms] in the fluorescent lamp), the measurement error caused by the flicker can be reduced.

The counter circuit 71a receives the input of the digital signal indicating the comparison result from the comparator 21 and receives the input of the reference pulse from the clock 72a.

The number of times the voltage of the photodiode 1 is reduced from the reference voltage to the comparison voltage and reset by the reset circuit 16, that is, the number of times the output of the photodiode 1 is within the reference pulse, Measures the number of times that the comparison voltage is reached, and outputs the number of times.

The number of times the output of the photodiode 1 reaches the comparison voltage within a predetermined time is proportional to the light intensity, and therefore the number of times indicates the light intensity.

In the digitizing circuit 77 of the first embodiment, the number of times of output becomes smaller as the light intensity becomes larger, whereas the number of times of output of the digitizing circuit 77a of the present embodiment increases as the light intensity increases. It becomes more suitable for the sense of the person using the sensor.

As described above, the digitizing circuit 77a includes reset means (reset circuit 16, switch 17, and reset circuit 16) for resetting the accumulated charge to an initial value each time the amount of charge accumulated by the photodiode 1 reaches a predetermined amount ), And the like. The counter circuit 71a functions as count value generating means for generating, as a count value, the number of times the resetting means has been reset during a predetermined time measured by the clock signal.

Fig. 15 shows a timing chart of the digitizing circuit 77a according to the second embodiment.

The output (Fig. 15 (a)) of the photodiode 1 is reset to the reference voltage by the reset signal (Fig. 15 (c)) of the reset circuit 16, The larger the value, the faster the deterioration.

The comparison result (Fig. 15 (b)) outputted by the comparator 21 outputs 0 when the voltage of the photodiode 1 reaches the comparison voltage at the reference voltage, whereby the reset circuit 16 outputs the reset signal (Fig. 15 (c)).

The counter circuit 71a counts the voltage of the photodiode 1 while the reference pulse for generating the clock 72a is 1 (the measurement period of the number of times the photodiode of FIG. 15 (d) That is, the number of times the reset circuit 16 has reset the photodiode 1, and outputs the result.

In this way, in the digitizing circuit 77a, the number of resetting of the photodiode 1 increases as the light intensity increases, so that the number of pulses corresponding to the light intensity is obtained.

14 (b) is a diagram for explaining the configuration of the digital output light detecting circuit 75a according to the present embodiment.

The digital output photodetecting circuit 75a includes a digitizing circuit 77a for digitizing the output of the photodiode 1 and a digitizing circuit 78a for digitizing the output of the photodiode 2. The configuration of the digitizing circuit 78a is the same as that of the digitizing circuit 77a.

The difference calculating section 73 receives the outputs of the photodiodes 1 and 2 converted into digital values from the digitizing circuits 77a and 78a and calculates these differences by digital processing and outputs the calculated difference as digital values Output.

In this way, the digital output photodetecting circuit 75a can control the photodiodes 1 and 2 by a simple configuration using the counter circuit 71a and the clock 72a without using arithmetic logic such as an A / Can be digitized.

The digitizing circuit 77a according to the present embodiment includes a light receiving element for generating electric charges by the light received by the light receiving element and an electric charge accumulated in the light receiving element when the light receiving element accumulates a predetermined amount of electric charge Reset means for resetting the light receiving element, and a number output means for outputting the number of times the reset means has reset the light receiving element for a predetermined time.

The following effects can be obtained by the embodiment described above.

(1) The amount of charges accumulated in the photodiodes 1 and 2 can be made to correspond to the clock. Thereby, a count value corresponding to the amount of charges can be generated, and the amount of charges accumulated in the photodiodes 1 and 2 can be digitized.

(2) Because it can be digitized using simple elements such as the counter circuit 71 and the clock 72, it is not necessary to use a large-scale logic such as an A / D converter.

(3) Since it is not necessary to use an A / D converter or the like, the IC chip can be miniaturized.

(4) The time until the light-receiving element reaches the reference voltage is measured as a clock pulse, and the number of pulses can be outputted as a digital value.

(5) The number of times that the light receiving element reaches the reference voltage within a predetermined time made by the reference pulse can be measured and output as a digital value.

Various embodiments and modifications have been described above, but the following configuration can be provided by these.

(A) An embodiment of the optical detecting apparatus provides the following arrangement.

In the embodiment relating to the light detecting device, the following arrangement can be obtained.

A first light receiving element for generating electric charges by the light received and having a spectroscopic characteristic different from that of the first light receiving element; A second light receiving element for receiving the electric charge accumulated in the first light receiving element and the second light receiving element; accumulating means for accumulating the generated electric charge in the light receiving element and the second light receiving element; difference acquiring means for acquiring a difference between the electric charges accumulated in the first light receiving element and the second light receiving element; And a differential output means.

(Second Configuration) The light detecting device according to the first configuration is characterized in that the accumulating means accumulates the electric charges by electrically opening predetermined electrodes of the first light receiving element and the second light receiving element .

(Third Configuration) The first light receiving element and the predetermined electrode of the second light receiving element are connected to a constant voltage source for resetting the electric charge accumulated in these light receiving elements through a predetermined switch, Wherein the predetermined electrode is electrically opened by turning off the switch. ≪ Desc / Clms Page number 24 >

(Fourth Configuration) The second configuration is characterized in that the difference acquisition means acquires the difference of the accumulated electric charges by the predetermined inter-electrode voltage difference between the first light reception element and the second light reception element , Or the third configuration.

(Fifth Configuration) A resetting means for resetting the charges accumulated in the first light receiving element and the second light receiving element by connecting the predetermined electrodes of the first light receiving element and the second light receiving element to a predetermined constant voltage source And a light receiving element that emits light.

(Sixth Configuration) The optical detecting apparatus according to any one of the first to fifth configurations, characterized by comprising changing means for changing the time during which the accumulating means accumulates charges in accordance with the intensity of light.

(Seventh Configuration) The optical pickup apparatus according to any one of the first to sixth configurations, characterized in that the difference acquisition means includes drive means for driving the difference output means at a timing at which the difference output means outputs the difference Device.

(Eighth Constitution) The image forming apparatus according to any one of the first to seventh configurations, characterized by comprising a mitigating means for alleviating the fluctuation caused in the difference output by the difference outputting means in accordance with the variation of the light intensity emitted by the light source And the light detecting device.

(Ninth Arrangement) An image display apparatus according to any one of the first to eighth configurations, an image display means for displaying an image, and an image display means for displaying the brightness And brightness adjusting means for adjusting the brightness of the image display means in accordance with the determined brightness.

(B) The first embodiment related to the photodetecting semiconductor device provides the following arrangement.

(First Configuration) A photodetecting semiconductor device for detecting light intensity by using a difference between a charge accumulated in a first photodetector and a charge stored in a second photodetector having a spectroscopic characteristic different from that of the first photodetector , The first light receiving element is composed of a semiconductor substrate composed of a first conductivity type semiconductor and a first conductive layer made of a second conductivity type semiconductor formed over a predetermined depth from the surface of the semiconductor substrate, The second light receiving element is composed of the semiconductor substrate and a second conductive layer made of a second conductive semiconductor formed from a surface of the semiconductor substrate to a depth deeper than the predetermined depth, Wherein a surface of the second conductive layer is provided with an electromagnetic wave shielding layer having conductivity so that light is transmitted therethrough.

(Second Configuration) The photodetecting semiconductor device according to the first configuration is characterized in that the electromagnetic wave shield layer is composed of a first conductivity type semiconductor.

(Third Configuration) The photodetecting semiconductor device according to the first configuration is characterized in that the electromagnetic wave shield layer is made of polysilicon.

(Fourth Structure) A photodetector is connected to the photodetecting semiconductor device described in the first, second, or third constitution, in which the first photodetection element and the second photodetection element generate the light receiving element An accumulation means for accumulating charge, a difference acquisition means for acquiring a difference between the stored charges, and a difference output means for outputting the obtained difference.

(Fifth Configuration) An image display apparatus according to the fourth configuration, an image display means for displaying an image, a brightness determination means for determining the brightness of the outside world using the output of the optical detection apparatus, And luminance adjusting means for adjusting the luminance of the image displaying means.

(C) The second embodiment related to the photodetecting semiconductor device provides the following arrangement.

(First Configuration) A photodetecting semiconductor device for detecting light intensity by using a difference between a charge accumulated in a first photodetector and a charge accumulated in a second photodetector, wherein the first photodetector is a first photodetector And a first conductive layer made of a second conductivity type semiconductor formed over a predetermined depth from a surface of the semiconductor substrate, wherein the second light receiving element is made of a semiconductor material, And a second conductive layer of a second conductivity type semiconductor formed from a surface of the semiconductor substrate to a predetermined depth, wherein a filter layer is formed on a surface of the first conductive layer, the filter layer having a light transmittance depending on a wavelength of light, Wherein a filter layer having a dependency different from that of the filter layer is formed on the surface of the second conductive layer or is not formed on the surface of the second conductive layer. Value.

(Second Configuration) The photodetecting semiconductor device according to the first configuration is characterized in that the filter layer has conductivity.

(Third Configuration) The photodetecting semiconductor device described in the first or second configuration is characterized in that the filter layer is composed of a first conductivity type semiconductor.

(Fourth Configuration) The photodetecting semiconductor device described in the first or second configuration is characterized in that the filter layer is made of polysilicon.

(Fifth Arrangement) A semiconductor light emitting device is connected to the photodetecting semiconductor device described in any one of structures 1 to 4, and charges accumulated in the first light receiving element and the second light receiving element of the photodetecting semiconductor device are accumulated And a difference outputting means for outputting the difference obtained by the difference obtaining means for obtaining the difference between the stored electric charges.

(Sixth Structure) An image display apparatus according to the fifth structure, an image display means for displaying an image, a brightness determination means for determining the brightness of the outside world using the output of the photo detection apparatus, And luminance adjusting means for adjusting the luminance of the image displaying means.

(D) An embodiment of the digital output optical detection circuit provides the following arrangement.

(First configuration) A light-receiving device comprising: a light-receiving element for generating electric charge by light received by light; accumulating means for accumulating charges generated in the light-receiving element; clock signal generating means for generating a clock signal; Count value generating means for generating a count value corresponding to the amount of the accumulated charge by corresponding to a clock signal and count value outputting means for outputting the generated count value, .

(Second Configuration) The digital output light described in the first configuration is characterized in that the count value generation means generates, as a count value, the number of clock signals generated until the accumulated charge changes from the initial value to a predetermined value Detection circuit.

(Third configuration), and reset means for resetting the accumulated charge to an initial value every time the amount of accumulated charge reaches a predetermined amount, and the count value generation means generates, for a predetermined time period measured with the clock signal, And the counted number of times of resetting by the resetting means is generated as a count value.

(Fourth Configuration) A digital output light detection circuit described in any one of the first configuration, the second configuration, and the third configuration is used, and a first count value corresponding to the amount of charge accumulated in the first light receiving element Count value acquiring means for acquiring a second count value corresponding to an amount of electric charge accumulated in a second light receiving element having a spectroscopic characteristic different from that of the first light receiving element; And a difference output means for outputting the calculated difference as a digital value.

(Fifth Configuration) An image display device according to the fourth configuration, an image display means for displaying an image, a brightness determination means for determining the brightness of the outside world using the output of the digital output light detection circuit, And a brightness adjusting means for adjusting the brightness of the image display means.

[Second Embodiment of Photodetecting Apparatus]

The photodetecting device 10 (Fig. 3) of the present embodiment sets the cathode terminals of the same photodiodes 1 and 2 to the open-ended state, and detects the charges accumulated in the photodiodes 1 and 2 for a predetermined period of time.

At this time, an optical filter for shielding infrared rays and ultraviolet rays is arranged on the photodiode 1, so that visible light reaches the photodiode 1.

On the other hand, a light-shielding layer for shielding infrared rays, ultraviolet rays and visible light is disposed on the photodiode 2 so that light does not reach the photodiode 2, and when light is not incident on the photodiode 2, Charge is detected.

The electric charge induced (induced) in the photodiode 2 when no light is incident is a dark charge (dark charge) detected as a dark current when it is detected as a current.

In the present embodiment, the cathode terminals of the photodiodes 1 and 2 are opened, and the desired light intensity is detected by removing dark charge noise components from the difference of the charges accumulated in the cathode terminals of the photodiodes 1 and 2 for a predetermined period of time.

16 is a view showing an example of a semiconductor device in which a photodiode used in the present embodiment is formed.

The semiconductor device 6e has the same configuration as the semiconductor device 6 shown in Fig. 1, and includes, for example, a P-type substrate 3 formed of a single crystal of silicon and formed of P type, Type layers 4 and 5, which are regions of the n-type layers 4 and 5, respectively.

The N-type layers 4 and 5 are formed over a predetermined depth from the surface of the P-type substrate 3 and the N-type layer 4 and the N-type layer 5 are formed at the same depth.

The photodiode 1 is constituted by the N-type layer 4 and the P-type substrate 3 and the photodiode 2 is constituted by the N-type layer 5 and the P-

The photodiodes 1 and 2 have the same spectral characteristics because they have the same configuration.

An optical filter 101 for shielding infrared light and ultraviolet light is disposed on the photodiode 1 and a light shielding layer 102 for shielding infrared light, ultraviolet light and visible light is disposed on the photodiode 2.

The light incident on the photodiode 1 is filtered by the optical filter 101, and visible light, from which infrared rays and ultraviolet rays are removed, reaches the light-receiving surface of the photodiode 1.

On the other hand, light (infrared light, ultraviolet light, and visible light) incident on the photodiode 2 is shielded by the light shielding layer 102 and can not reach the light receiving surface of the photodiode 2.

In this way, in the semiconductor device 6e, the photodiode 2 not provided with the light is formed in order to remove the dark charge noise generated in the photodiode 1.

That is, the photodiode 1 and the photodiode 2 generate the same dark charge because they have the same configuration including the depth of the N-type layer.

Therefore, when the photodiode 1 detects light, it becomes the same as the dark charge generated in the dark photodiode 2 generated as noise in the photodiode 1, The charge generated in the photodiode 1 can be obtained by the incident light by removing the dark charge of the photodiode 2 from the generated charge.

Fig. 17 is a diagram schematically showing the spectroscopic characteristics using the difference of the photodiodes 1 and 2. Fig. Note that FIG. 17 is not necessarily drawn strictly because it is a schematic diagram for explaining the concept.

The vertical axis represents the output (current, voltage, etc.) generated by the photodiode, and the horizontal axis represents the wavelength of the incident light. Further, the light intensity of the incident light is assumed to be constant.

In the photodiode 1, visible light is incident on the optical filter 101 to generate charges and dark charges due to visible light. By removing dark charges generated in the photodiode 2 from the visible light, A charge is obtained.

When the voltage by this electric charge is measured, as shown in Fig. 17, the sensitivity in a visible light region of about 400 [nm] to 700 [nm] is obtained.

As described above, in the photodiode 1, since the output from the light transmitted through the optical filter 101 is obtained, if the optical filter 101 is configured to transmit ultraviolet light and shield other light, (6e) can be used as an ultraviolet sensor, and when infrared light is transmitted and other light is shielded, it can be used as an infrared sensor.

That is, by configuring the optical filter 101 so as to transmit light of a wavelength to be observed, it can be used as a sensor for detecting light of a desired wavelength band.

The configuration of the photodetector 10 using the semiconductor device 6e is the same as that of Fig.

When the optical filter 101 is disposed on the light-receiving surface of the photodiode 1 of Fig. 3 and the light-shielding layer 102 is disposed on the light-receiving surface of the photodiode 2, 10) is obtained.

Since the operation of the photodetector 10 using the semiconductor device 6e is the same as that of Fig. 3, the description thereof will be omitted.

The configuration of the semiconductor device 6e and the optical detection device 10 has been described above. In the semiconductor device 6e, however, the optical filter 101 has the first light-shielding function for shielding light other than the incident light of a desired wavelength And the light-shielding layer 102 functions as a second light-shielding means for shielding all the incident light.

Therefore, in the semiconductor device 6e, the photodiode 1 and the optical filter 101 function as a first light-receiving element forming a first light-shielding means for shielding incident light other than the incident light of the desired wavelength , The photodiode 2 and the light-shielding layer 102 function as a second light-receiving element formed with second light-shielding means for shielding incident light.

In the photodetector 10 using the semiconductor device 6e, since the photodiode 1 and the photodiode 2 are charged by the switches 17 and 18, And a storage means for storing charges generated in one light receiving element and the second light receiving element.

In the photodetector 10 using the semiconductor device 6e, since the incident light is output from the difference circuit 15 as the difference of the amount of charge accumulated in the photodiodes 1 and 2, the photodetector 10 And difference obtaining means for obtaining the difference between the amounts of charges accumulated in the first light receiving element and the second light receiving element and output means for outputting the difference as the amount of charge of the incident light corresponding to the desired wavelength.

Since the configurations of the photodiode 1 and the photodiode 2 are the same, the first light receiving element and the second light receiving element have the same light receiving and storage characteristics.

As described above, the accumulating means of the photodetecting apparatus 10 using the semiconductor device 6e can be realized by the use of a predetermined electrode (cathode) of the first photodetector (photodiode 1) and the second photodetector (photodiode 2) Terminals) are electrically opened to accumulate electric charges.

The predetermined electrodes of the first light receiving element and the second light receiving element are connected to a constant voltage source (DC power supply 19) for resetting the charges accumulated in these light receiving elements through predetermined switches (switches 17 and 18) , And the accumulating means electrically opens the predetermined electrode by turning off the switch.

The difference obtaining means (the differential circuit 15) is a circuit for obtaining the difference between the predetermined electrodes (cathode terminals) of the first light receiving element (photodiode 1) and the second light receiving element (photodiode 2) (Photodiode 1) and the second photodetector (photodiode 1), and the photodetector 10 acquires the difference of the accumulated charge by turning on the switches 17 and 18, (Cathode terminal) of the second light receiving element (2) is connected to a predetermined constant voltage source (DC power supply 19), thereby resetting the charges accumulated in the first light receiving element and the second light receiving element have.

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That is, in the semiconductor device 6e, since the photodiode 2 removes the dark noise generated in the photodiode 1 and improves the detection accuracy of the photodiode 1, The photodiode 1 is performed.

This makes it possible to detect visible light by using the photodiode 1 and the optical filter 101 without using the photodiode 2 although the accuracy is lower than when the photodiode 2 is used.

In this case, the amount of charge stored in the photodiode 1 is detected by the photodetector 10 (since there is no photodiode 2), the difference circuit 15 outputs the charge stored in the photodiode 1 , The charge amount itself is set as the detection value.

In this case, a light receiving element (photodiode 1) for applying a semiconductor device 6e excluding the photodiode 2 to the photodetector 10 to generate charges by the incident light, An accumulating means for accumulating the charges in the device, and an output means for outputting the amount of charge of charges corresponding to the incident light of the desired wavelength accumulated in the accumulating means.

(Optical filter 101) for shielding light other than incident light of a desired wavelength incident on the light receiving element, and the output means outputs the amount of the electric charge accumulated in the accumulating means to the light receiving element And output as the charge amount.

The accumulation means (switch 17) accumulates charge by electrically opening a predetermined electrode (cathode terminal) of the light receiving element (photodiode 1), or a predetermined electrode of the light receiving element, (DC power supply 19) for resetting the electric charges accumulated in these light receiving elements through a predetermined switch (switch 17), and the accumulating means electrically turns off the switch so that the predetermined electrode is electrically And the resetting means for resetting the charge accumulated in the light receiving element by connecting the predetermined electrode of the light receiving element to the predetermined constant voltage source can be realized by using the photodetecting device using the semiconductor device 6e 10).

4 are diagrams for explaining the case where the photodiodes 1 and 2 of the semiconductor device 6e are saturated.

The photodiode 1 rapidly charges the electric charge as the light to be received becomes strong. Therefore, if the illuminance is large, the output of the photodiode 1 may become saturated before the illuminance judging section 12 detects the output of the difference circuit 15, so that the correct value may not be measured.

4A is a schematic diagram for explaining a case where the output of the photodiode 1 is saturated at the time of reset.

First, when the photodiodes 1 and 2 are connected to the DC power supply 19 (Fig. 2) and the voltage of the cathode terminal is set to the reference voltage and then the switches 17 and 18 are turned off, As shown in Fig.

Light transmitted through the optical filter 101 is incident on the photodiode 1 while light is not incident on the photodiode 2 by the light shielding layer 102. Therefore, (2) The voltage drops sooner.

In Fig. 18 (a), since the light intensity is large, the output of the photodiode 1 is saturated before reaching the reset time t1.

Assuming that the illuminance determining section 12 detects the output of the difference circuit 15 immediately before resetting, at the reset time t1, the photodiode 2 is detected to be the voltage E1 due to dark discharge, ), The output value is saturated, so that the detection value according to the light intensity can not be obtained.

Thus, as shown in Fig. 18 (b), reset is performed when the voltage of the photodiode 1 reaches a predetermined comparison voltage.

In the example of Fig. 18 (b), the photodiode 1 is reset at time t2 when the comparison voltage becomes the comparison voltage. In this case, the voltage of the photodiode 2 is E2.

Therefore, the photodiode 1 can output a voltage corresponding to the light intensity.

In order to perform such an operation, the semiconductor device 6e may be inserted into the photodetector 10a shown in Fig.

5, the voltage of the photodiode 2 is compared with the comparison voltage of the direct current power supply 22. In the case of the semiconductor device 6e, the voltage of the photodiode 1 is compared with the comparison voltage 5, the photodiode 1 and the photodiode 2 are exchanged with each other.

The operation of the photodetection apparatus 10a in which the semiconductor device 6e is sandwiched is the same as that described above with reference to FIG.

In this manner, the accumulating means can be provided with a changing means for changing the time for accumulating the electric charge in accordance with the light intensity.

By applying the semiconductor device 6e to the photodetecting apparatus 10b shown in Fig. 6, the illuminance judging section 12 intermittently drives them only when detecting the difference of the photodiodes 1 and 2 It can also be configured to save power consumption.

The operation of the photodetector 10b in this case is as described above with reference to FIG.

In this way, the difference acquisition means (difference circuit 15) can be configured to include drive means (timer clock 31) for driving the difference output means at the timing of outputting the difference.

By applying the light detecting device 10c shown in Fig. 7 to the semiconductor device 6e, the influence of the flicker of the light source can also be reduced.

The operation of the photodetector 10c in this case is as described above with reference to FIG.

As described above, it is also possible to provide an attenuation means (an integrating circuit 41) for alleviating the fluctuation caused in the difference outputted by the differential outputting means (the differential circuit 15) by the fluctuation of the light intensity emitted by the light source.

In addition, as shown in Fig. 19, a thin film electrode having light transmittance may be disposed on the photodiode so that the photodiode is shielded from electromagnetic noise from the outside.

Fig. 19 is a diagram showing the structure of the semiconductor device 6f according to the present embodiment, and corresponds to Fig.

The same components as those in Fig. 8 are denoted by the same reference numerals, and the description thereof is simplified or omitted.

The semiconductor device 6f is a photodetecting semiconductor device and the N type layers 4 and 5 are formed on the P type substrate 3 like the semiconductor device 6e.

Here, the photodiode 1 includes a semiconductor substrate (P-type substrate 3) composed of a semiconductor of a first conductivity type (P-type in this case) and a second conductive (The N-type layer 4) made of a semiconductor (here, N-type) semiconductor and the photodiode 2 functions as a first light receiving element composed of a semiconductor substrate (P-type substrate 3) And a second conductive layer (N-type layer 5) made of a second conductive semiconductor formed over a predetermined depth from the surface of the semiconductor substrate.

On the upper surfaces of the N-type layers 4 and 5, thin P-type layers 51, 51, ... are formed.

The P-type layer 51 transmits the light to be detected and shields the electromagnetic wave.

As described above, light is transmitted through the surface of the first conductive layer (N-type layer 4) and the second conductive layer (N-type layer 5) to form a conductive electromagnetic wave shielding layer (P- Is formed.

Further, the P-type layer 51 can exhibit a shielding function more effectively by being grounded.

The aluminum wirings 52 and 52 connected to the n-type layers 4 and 5 are connected to the n-type layers 4 and 5 via the n + -type thick layer 55 having an n-type concentration.

A wiring through hole is formed in the P-type layer 51, and an aluminum wiring 52 is formed in the through hole.

The P-type substrate 3 is connected to the aluminum wiring 54 by a P + layer 56 having a thick P-type concentration and is grounded.

On the light-receiving surface, the light-shielding aluminum 53, 53, ... is formed on the region where the photodiode is not formed and on the photodiode 2 to block the incidence of light.

Thus, in this example, the light-shielding aluminum 53 functions as the light-shielding layer 102. [

An optical filter 101 is disposed on the photodiode 1 to obtain desired spectral characteristics.

The luminance of the liquid crystal display of the portable telephone can be adjusted by using the semiconductor device 6e and the light detecting device 10 constructed as described above.

In this case, the brightness of the visible light of the outside world is measured by the photodetector 10, and for example, when the outside world is bright, the brightness of the screen is low, and when the outside world is dark, the brightness of the screen is high.

In this way, the image display means for displaying an image, the brightness determination means for determining the brightness of the outside world using the output of the photodetection device, and the brightness adjustment means for adjusting the brightness of the image display means in accordance with the determined brightness A display device may be provided.

As described above, the optical detection device can be constructed by applying the following digital output optical detection circuit to the semiconductor device 6e.

(At least one of a photodiode 1 having an optical filter 101 and a photodiode 2 having a light-shielding layer 102) for generating electric charges by light received therefrom, A clock signal generation means for generating a clock signal; and a clock signal generation means for generating a count value corresponding to the amount of the accumulated charge by associating the accumulated charge amount with the generated clock signal And count value output means for outputting the count value generated by said count value output means.

(Second Configuration) The digital output light described in the first configuration is characterized in that the count value generating means generates, as a count value, the number of clock signals generated until the accumulated charge changes from an initial value to a predetermined value Detection circuit.

(Third configuration), and reset means for resetting the accumulated charge to an initial value every time the amount of accumulated charge reaches a predetermined amount, and the count value generation means generates, for a predetermined time period measured with the clock signal, And the counted number of times of resetting by the resetting means is generated as a count value.

(Fourth Configuration) A digital output light detection circuit described in any one of the first configuration, the second configuration, and the third configuration is used, and a first count value corresponding to the amount of charge accumulated in the first light receiving element Count value acquiring means for acquiring a second count value corresponding to an amount of electric charge accumulated in a second light receiving element having a spectroscopic characteristic different from that of the first light receiving element; And a difference output means for outputting the calculated difference as a digital value.

(Fifth Configuration) An image display device according to the fourth configuration, an image display means for displaying an image, a brightness determination means for determining the brightness of the outside world using the output of the digital output light detection circuit, And a brightness adjusting means for adjusting the brightness of the image display means.

According to the second embodiment of the light detecting device described above, the following effects can be obtained.

(1) By forming an optical filter 101 that transmits visible light, which is light to be observed, and shields other light, to the photodiode 1, charges corresponding to visible light are accumulated in the photodiode 1, Can be obtained as a voltage.

(2) A photodiode 2 having the same structure as that of the photodiode 1 is formed so that all the light incident on the photodiode 2 is shielded to generate the same dark charge as the dark charge generated in the photodiode 1 .

(3) By taking the difference between the voltages of the photodiode 1 and the photodiode 2, it is possible to cancel the influence due to the dark current generated in the photodiode 1, and obtain desired spectral characteristics.

(4) Since the photodiode 1 and the photodiode 2 have the same structure, the manufacturing is easy and the manufacturing cost can be reduced.

(5) By appropriately forming the spectroscopic characteristics of the optical filter 101, a photodetecting device can be constructed for various types of light. For example, it can be used as an ultraviolet sensor.

One … Photodiode
2 … Photodiode
3 ... P-type substrate
4 … N-type layer
5 ... N-type layer
6 ... Semiconductor device
7 ... N-type layer
10 ... Optical detection device
12 ... Illuminance judgment section
13 ... Amplifier
14 ... Amplifier
15 ... Differential circuit
16 ... Reset circuit
17 ... switch
18 ... switch
19 ... DC power
21 ... Comparator
22 ... DC power
31 ... Timer clock
32 ... switch
33 ... switch
41 ... Integral circuit
51 ... P-type layer
57 ... The polysilicon layer
71 ... Counter circuit
72 ... Clock
73 ... Difference operator
75 ... Digital output photodetection circuit
77 ... Digitizing circuit
78 ... Digitizing circuit
101 ... Optical filter
102 ... Shading layer

Claims (17)

A light receiving element for generating an electric charge by the incident light,
Accumulating means for accumulating the generated charge in the light receiving element,
An output means for outputting a charge amount of a charge corresponding to incident light of a desired wavelength accumulated by the accumulating means;
And changing means for changing the time for the accumulation means to store the charge in the light-receiving element in accordance with the intensity of the light,
The light receiving element includes a first light receiving element formed with a first light shielding means for shielding light other than incident light of the desired wavelength and a second light shielding means for shielding all the incident light, ≪ / RTI >
Wherein the accumulating means accumulates the generated charges in the first light receiving element and the second light receiving element,
Wherein said output means includes a difference acquiring means for acquiring a difference between the amounts of charges accumulated in said first light receiving element and said second light receiving element and a difference outputting means for outputting a difference between the amounts of electric charges as a charge amount of charges corresponding to the incident light of the desired wavelength And a light source for emitting light. The method according to claim 1,
Wherein the first light receiving element and the second light receiving element have the same light receiving and storage characteristics. 3. The method according to claim 1 or 2,
Wherein the changing means shortens the time for the accumulating means to accumulate electric charge as the intensity of light incident on the first light receiving element and the second light receiving element becomes strong. The method of claim 3,
Wherein the first light receiving element and the second light receiving element are configured such that a predetermined electrode is reverse biased to a reference voltage in an initial state and the predetermined electrode is electrically opened to accumulate the charge, Lt; / RTI >
When the voltage of the light receiving element on the side where the voltage drop of the first light receiving element and the second light receiving element is larger than the reference voltage and reaches a predetermined comparison voltage, And the accumulating means shortens the time for accumulating the electric charge by resetting the second light receiving element to the initial state. 5. The method of claim 4,
Wherein the difference acquiring means acquires the difference of the accumulated electric charges by the predetermined inter-electrode voltage difference between the first light receiving element and the second light receiving element. 3. The method according to claim 1 or 2,
And drive means for driving the difference acquisition means at a timing at which the difference output means outputs the difference. 3. The method according to claim 1 or 2,
And an alleviating means for alleviating a fluctuation caused in a difference output by said difference outputting means due to a variation in light intensity emitted by said light source. An optical pickup apparatus comprising: the optical pickup apparatus according to claim 1 or 2;
An image display means for displaying an image,
Brightness determining means for determining the brightness of the outside world using the output of the light detecting device;
And brightness adjusting means for adjusting the brightness of the image display means in accordance with the determined brightness. delete delete delete delete delete delete delete delete delete

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